STAR QA Board

["Van Buren, Gene" <gene@bnl.gov>]

Hi, Geary

On Dec 27, 2021, at 1:02 PM, Geary Eppley <eppley@rice.edu> wrote:

The central Vx vs Vy central distribution shown Friday has a radius of order 1mm. The L4 distribution has a radius of order 1 cm. Do you know what causes that difference?

I do not know exactly what L4 is doing, but my best guess is that they are using no BeamLine constraint at all.

We are interested in VPD-TPC Vz offset to see if any adjustments need to be made. L4 consistently shows and offset of -2 cm or less. The RMS is just slightly worse than Run 17, which is not bad considering the current problems with the active splitter.

What offset do you see in your analysis?

I'm attaching a histogram of (Vtx_z,tpc - Vtpx_z,vpd) from the data I used to determine the BeamLine last Tuesday. Hope that's useful.

-Gene